People forget that Mark Buehrle's success this year is really just an extension of the 2nd half of last year. He has just as much WAR over the past year as James Shields who most people would consider an ace. Factor in that the guy is made of titanium and I think this guys well worth the 20m a season. His current pace is probably unsustainable but I dont think its a stretch to assume he'll probably end this season with a sub 3.50 ERA in a division many people thought he no longer had the ability to pitch in.